The disclosure of Japanese Patent Application No. 2007-096533 filed on Apr. 2, 2007, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a vehicular control apparatus and a vehicular control method.
2. Description of the Related Art
In a vehicle such as an automobile, rotation from an internal combustion engine side is transmitted to the wheel side via an automatic transmission. This automatic transmission includes a torque converter and a gear shift mechanism, and establishes a plurality of gears with different gear ratios by selectively applying a plurality of apply elements such as clutches and brakes so as to switch the power transmitting path in the gear shift mechanism.
The apply elements such as the clutches and brakes operate based on the hydraulic pressure of hydraulic fluid that is supplied through a hydraulic control circuit, and are switched between an applied state and a released state by adjusting this hydraulic pressure through controlling the operation of various solenoid valves provided in this hydraulic control circuit. The gear (i.e., speed) of the automatic transmission is shifted by operating the apply elements in the following manner. That is, in response to a shift command, hydraulic pressure applied to a predetermined apply element is reduced such that that apply element releases (hereinafter this apply element will be referred to as the “release-side apply element”), while hydraulic pressure applied to another predetermined apply element is increased according to a hydraulic pressure command value such that that apply element applies (hereinafter this apply element will be referred to as the “apply-side apply element”). The apply and release of these apply elements in this way results in a gear shift that is based on the shift command.
Here, when applying the apply-side apply element while releasing the release-side apply element for an upshift, i.e., a shift into a higher gear, in the automatic transmission, the inertia phase that results from applying the apply-side apply element must start at just the right time in order for that upshift to be smooth. Incidentally, the inertia phase is a period of time from when the input rotation speed of the automatic transmission starts to fall after the apply-side apply element starts to be applied, until the apply-side apply element is completely applied. The timing at which this inertia phase starts (also referred to as the “inertia phase start timing”) changes depending on the hydraulic pressure command value, which is the command value for the hydraulic pressure applied to the apply-side apply element. That is, as the hydraulic pressure command value increases, the hydraulic pressure applied to the apply-side apply element increases faster so the inertia phase starts sooner. Conversely, as the hydraulic pressure command value decreases, the hydraulic pressure applied to the apply-side apply element increases slower so the inertia phase starts later.
Accordingly, when the inertia phase starts, the hydraulic pressure command value is increased or decreased so that the period of time from when an upshift command is output until the inertia phase starts comes to match a target value (i.e., which corresponds to an appropriate time to start the inertia phase), and that increased or decreased hydraulic pressure command value is learned as a learning value. Learning the hydraulic pressure command value in this way enables the hydraulic pressure command value to be optimized in order to make the period of time match the target value. The inertia phase is then able to be started at an appropriate timing by increasing the hydraulic pressure of the apply-side apply element based on that hydraulic pressure command value. Incidentally, the hydraulic pressure command value is prepared and learned for each type of upshift in the automatic transmission, e.g., for an upshift from 1st gear into 2nd gear, an upshift from 2nd gear into 3rd gear, an upshift from 3rd gear into 4th gear, an upshift from 4th gear into 5th gear, and an upshift from 5th gear into 6th gear, and the like.
Also, in addition to learning the hydraulic pressure command value, other types of learning related to shifting gears in an automatic transmission are also known. For example, Japanese Patent Application Publication No. 11-37267 (JP-A-11-37267) describes technology that learns a release rate of an apply element to be released from an applied state in response to a shift command, so that the release rate becomes a value that prevents overshooting of the input rotation speed of the automatic transmission. Incidentally, this learning is prohibited when a throttle valve opening amount changes in response to an accelerator operation.
Also, Japanese Patent No. 3536537 describes technology that learn-corrects the apply pressure decrease rate, the hold time, and the rapidly decreasing value of an apply element to be released from an applied state in response to a shift command. Incidentally, this learning is prohibited when the engine speed is overshot due to the wheels slipping during an upshift.
Further, Japanese Patent No. 2615889 describes technology that learns a line pressure, which is the base pressure of hydraulic fluid supplied to apply elements, such that the inertia phase period, which is the period of time from when an apply element that is to be applied from a released state starts to apply in response to a shift command, until that apply element is completely applied, is appropriate. Incidentally, this learning is prohibited when the input characteristics of the automatic transmission with respect to engine load are different from what they normally are, such as when driving an air-conditioner compressor in the vehicle, when driving power steering in the vehicle, or when the engine is running in an environment where the air pressure is low.
When applying the apply-side apply element to shift the automatic transmission into a higher gear, the force required to apply that apply-side apply element can be reduced by reducing the input rotation speed of the automatic transmission (i.e., the speed of the internal combustion engine), which is done by reducing the output torque of the engine for that apply operation. Further, heat generated from friction when applying the apply-side apply element can also be kept low. In order to obtain these kinds of effects, when applying the apply-side apply element to shift the automatic transmission into a higher gear, the throttle valve of the internal combustion engine is controlled so that the opening amount thereof decreases to reduce the output torque of the internal combustion engine for that apply operation.
However, even when the throttle valve is controlled in this way, i.e., such that the opening amount thereof is reduced, a certain amount of delay until the output torque of the internal combustion engine actually decreases from reducing the amount of intake air drawn into the engine by reducing the opening amount of the throttle valve is unavoidable. Accordingly, the control to reduce the opening amount of the throttle valve is started somewhat early taking into account this delay in the reduction of output torque from the internal combustion engine. However, if the control to reduce the opening amount of the throttle valve is started early, when the input rotation speed of the automatic transmission (i.e., the engine speed) decreases as a result of the decrease in output torque from the internal combustion engine following execution of that control, that decrease in the input rotation speed of the automatic transmission may be erroneously interpreted as the start of the inertia phase, and as a result erroneous learning of the hydraulic pressure command value may be performed.
Incidentally, although JP-A-11-37267, Japanese Patent No. 3536537, and Japanese Patent No. 2615889 all mention the prohibiting of learning, even if the technologies relating to the prohibiting of learning in those publications were to be employed, erroneous learning of the hydraulic pressure command value could not be prevented. This is because the learning targets in those publications are targets other than the hydraulic pressure command value described above, so even if learning according to the prohibiting conditions described in those publications is prohibited, the hydraulic pressure command value is still learned regardless of that fact when the control to reduce the opening amount of the throttle valve is executed.